framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/configuration/Rot13PasswordEncoder.java

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package org.apache.cayenne.configuration;

/**
 * The ROT-13 password encoder passes the text of the database password through a simple
 * Caesar cipher to obscure the password text. The ROT-13 cipher only processes letters --
 * numbers and symbols are left untouched. ROT-13 is also a symmetrical cipher and
 * therefore provides no real encryption since applying the cipher to the encrypted text
 * produces the original source text. See the Wikipedia entry on <a
 * href="https://en.wikipedia.org/wiki/Rot-13">ROT13</a> for more information on this
 * topic.
 * 
 * @since 3.0
 */
public class Rot13PasswordEncoder implements PasswordEncoding {

    public String decodePassword(String encodedPassword, String key) {
        return rotate(encodedPassword);
    }

    public String encodePassword(String normalPassword, String key) {
        return rotate(normalPassword);
    }

    /**
     * Applies a ROT-13 Caesar cipher to the supplied value. Each letter in the supplied
     * value is substituted with a new value rotated by 13 places in the alphabet. See <a
     * href="https://en.wikipedia.org/wiki/ROT13">ROT13</a> for more information.
     * <p>
     * A Unix command to perform a ROT-13 cipher is:
     * 
     * <pre>
     * tr "[a-m][n-z][A-M][N-Z]" "[n-z][a-m][N-Z][A-M]"
     * </pre>
     * 
     * @param value The text to be rotated.
     * @return The rotated text.
     */
    public String rotate(String value) {
        if (value == null) {
            return null;
        }

        int length = value.length();
        StringBuilder result = new StringBuilder();

        for (int i = 0; i < length; i++) {
            char c = value.charAt(i);

            // If c is a letter, rotate it by 13. Numbers/symbols are untouched.
            if ((c >= 'a' && c <= 'm') || (c >= 'A' && c <= 'M'))
                c += 13; // The first half of the alphabet goes forward 13 letters
            else if ((c >= 'n' && c <= 'z') || (c >= 'A' && c <= 'Z'))
                c -= 13; // The last half of the alphabet goes backward 13 letters

            result.append(c);
        }

        return result.toString();
    }

    /**
     * Small test program to run text through the ROT-13 cipher. This program can also be
     * run by hand to encode/decode values manually. The values passed on the command line
     * are printed to standard out.
     * 
     * @param args The array of text values (on the command-line) to be run through the
     *            ROT-13 cipher.
     */
    public static void main(String[] args) {
        Rot13PasswordEncoder encoder = new Rot13PasswordEncoder();

        for (String string : args) {
            System.out.println(encoder.rotate(string));
        }
    }
}